|Europe aims for endless energy
Tim Radford, science editor
Thursday November 27, 2003
Europe's scientists hope to mimic the power of the sun and create
limitless energy on Earth with the help of a £6bn experiment in the south
Ministers in Brussels gave the go-ahead yesterday for Iter, the world's
biggest and most ambitious fusion reactor, at Cadarache near
Aix-en-Provence. It will be 10 years in the making and, in its 20-year
operating life, researchers will experiment with a kind of slow hydrogen
bomb in the hope of extracting vast amounts of clean energy from tiny
amounts of heavy water.
Iter will replace Jet, the current joint European fusion research project,
based at Culham, Oxfordshire.
Sir Chris Llewellyn-Smith, head of the UK fusion programme, said
yesterday: "The Iter project will allow a major step towards an
inexhaustible source of environmentally friendly power."
Petroleum and coal deliver chemical energy liberated by the breaking of
chemical bonds in the form of fire. Nuclear fission of enriched uranium
exploits the energy released by the breakdown of a unstable heavy atom to
a lighter one. But the "ash" from a fission reaction is radioactive and it
stays too hot to handle for thousands of years.
The great prize has always been fusion power: the fusion of two hydrogen
atoms to make one of helium, releasing huge quantities of heat. Every
second, the sun converts 600m tonnes of hydrogen into helium and
illuminates and warms this planet from 90m miles away.
To do the same on Earth, engineers and physicists have to collect
deuterium and tritium - isotopes of hydrogen - and heat them to more than
100m C, many times hotter than the heart of the sun. At these temperatures
the heavy hydrogen would become a plasma, a ball of subatomic particles
which would fuse to become helium and a shower of neutrons and a supply of
heat. One kilogram of heavy hydrogen would supply the heat now generated
by 10m kg of fossil fuel. There would be no greenhouse gases, no soot, and
no long-lived radioactive waste. The oceans contain all the heavy hydrogen
such reactors would need.
Fusion power would, in theory, be safe, because the challenge is not to
stop a fusion reaction, but to keep it going. But that is the catch. If
plasma at 100m C so much as touched anything, it would go out like a
light. The trick is to keep tiny pellets of fuel suspended in a kind of
magnetic "bottle" in a sealed chamber. Then engineers would have to pump
blasts of laser fire at the pellets, compressing them to 20 times the
density of lead, at which point they would start to behave like tiny
stars, releasing a thermonuclear blast of neutrons to heat up a
containment wall many metres away.
Fusion's most ardent enthusiasts believe that a viable power plant is 30
years away. Iter is just another stage in the research.
Although the Cadarache site has Brussels' backing, the decision has yet to
be confirmed by the other partners in the project. These include Canada,
the US, Russia, Japan, South Korea and China. There is one other candidate
site - at Rokkashomura in Japan - and the final decision could be made in
Washington next month.